Slash-and-Burn Agriculture in the Wet Coastal Lowlands of Papua New Guinea: Response of Birds, Butterflies and Reptiles

Abstract

Twenty-two plots were studied in the humid coastal lowlands of Northern PNG to describe succession of plants, birds, butterflies and reptiles from gardens to forest. The first axis of a detrended correspondence analysis of floristic lists from twenty vegetated plots was strongly positively correlated with estimates of time since gardening, canopy height and cover, total basal area of stems greater than 3 m in height, leaf litter, and total concentrations of S, C and N in the top 5 cm of soil. Grass cover, soil pH and available K were negatively correlated. Burning of slashed secondary forest was found to increase to soil P, available Ca, cation exchange capacity, electrical conductivity, S, C and N to levels in primary forests. Bird, butterfly and reptile species diversity increased along the successional gradient. This response was least marked with reptiles. Niche breadths of these faunal groups decreased with later successional stages. The primary forests support birds which are specialist feeders, particularly frugivores, nectarivores and branch gleaners. Obligate granivores were restricted to a grassy early successional plot, which was identified as an outlier in the analysis and which had atypical soil attributes. A substantial number of plant species was restricted to, or occurred in, early successional stages, in contrast to the small proportion of animal species that used such sites. This may reflect a long history of intermediate disturbance (i.e. forest gaps) and relatively little widespread disturbance. This specialization renders the fauna vulnerable to increasing anthropogenic habitat modification.